Environmental Stewardship (ES) is voluntary action on behalf of the environment. ES is typically practiced at environmental nonprofit organizations that offer stewardship programs. Because these programs are managed by individual organizations, relatively little external research exists on their impacts, e.g., diffusing norms and behaviors of ES more broadly across society. Responding to that research gap, this paper studies change in the environmental outlooks and behaviors of participants at two partner nonprofits in Texas using surveys (n=407) and interviews (n=5). Three categories of changes in environmental behavior are assessed: Natural Areas, Environmental Activism, and Water Awareness. Findings demonstrate that participation was linked to pro-environmental changes in all categories for the survey respondents. Follow-up interviews allowed us to capture additional aspects of ES not addressed in the survey. In all, ES can lead to greater uptake in selected pro-environment actions, higher awareness of environmental issues, and greater appreciation for natural amenities.